Dispensing modules are commonly used to dispense viscous liquids, such as hot melt liquid adhesives, in a variety of dispensing applications for manufacturing products and product packaging. Conventional dispensing modules include a dispensing assembly having either an electrically actuated valve assembly or an electro-pneumatically actuated valve assembly that regulates a flow and discharge of the liquid adhesive from the dispensing module. The valve includes a valve element that is moveable within the dispensing assembly for selectively displacing a needle tip relative to a valve seat within a nozzle of the dispensing module. In turn, the liquid adhesive discharges from the nozzle. The nozzle also receives a pressurized gas and discharges the pressurized gas about the liquid adhesive for spraying the liquid adhesive as a plurality of droplets according to a pattern, such as a circular pattern.
Conventional nozzles often receive the pressurized gas through a gas inlet asymmetrically positioned within the nozzle for routing the pressurized gas through the dispensing module and toward the nozzle. While such routing may be convenient for circumventing the valve element projecting through a central portion of the nozzle, the pressurized gas tends to flood the nozzle unevenly. More particularly, the pressurized gas flowing toward the gas outlet is susceptible to inconsistent air velocities and inconsistent pressure distributions as the pressurized gas approaches the gas outlet. For example, the gas inlet may be positioned at one end of a gas passage and must flow laterally across the valve before then flowing axially toward a gas outlet of the nozzle. As such, a flow of the pressurized gas rushing toward the gas outlet on one lateral side of the valve may be traveling at a different velocity than a flow of the pressurized gas rushing toward the gas outlet on an opposing lateral side of the valve.
In contrast to the pressurized gas, the liquid adhesive discharges from the nozzle generally consistently and uniformly. Thus, as the pressurized gas of differing velocities impacts the liquid adhesive, the droplets of liquid adhesive spray from the nozzle in an inconsistent pattern that differs from the intended pattern. For example, the intended pattern may be circular, but the final pattern may be irregular and/or uneven.
There is a need for an adhesive dispensing module and method of spraying a liquid, such as a hot melt liquid adhesive, that generates a consistent, predetermined spray pattern of liquid droplets that addresses present challenges and characteristics such as those discussed above.